For the majority of older, early-stage breast cancer patients, radiation therapy following breast conserving surgery may help prevent the need for a later mastectomy, according to research from The University of Texas MD Anderson Cancer Center.

The findings, published in the journal Cancer, are contrary to current national treatment guidelines, which recommend that older women with early stage, estrogen-positive disease be treated with lumpectomy followed by estrogen blocker therapy alone -- and forgo radiation therapy post-surgery.

The potential benefit of radiation in this patient population has been the focus of much research over the past decade, said Benjamin Smith, M.D., assistant professor in the Department of Radiation Therapy at MD Anderson and the study’s corresponding author.

In 2004, a major study found that women who received tamoxifen alone, compared to tamoxifen and six weeks of radiation, had a slightly higher incidence of breast cancer recurrence. Yet, there was no difference in mastectomy rates or survival among the two cohorts, said Smith. Based on these findings, the NCCN adjusted its treatment guidelines, and radiation therapy following lumpectomy was no longer recommended. Smith then followed up this guideline-changing research with a population-based study, confirming the earlier findings with respect to breast cancer recurrence.

“The motivation for this new research was to do a similarly designed study with longer term follow up,” said Smith. “We wanted to do a 10-year update, focusing specifically on the mastectomy question. The fundamental reason it was determined that women didn’t need radiation was because the additional therapy did not change mastectomy rates.”

For the population-based study, Smith and his colleagues derived a cohort of Medicare patients from the National Cancer Institute’s Surveillance, Epidemiology and End Results (SEER) registry who would have been eligible for the 2004 study. The researchers identified 7,403 patients ages 70-79 treated with a lumpectomy for early-stage estrogen-positive breast cancer. All were diagnosed between 1992 and 2002, with follow up through 2007. Of the 7,403 women, 88 percent received radiation after their lumpectomy.

Within 10 years of their treatment, 6.3 percent of the women who did not receive radiation therapy had a mastectomy, likely because of a breast cancer recurrence, says Smith, compared to 3.2 percent who had the additional treatment. In patients with high-grade tumors, regardless of other factors such as age and/or tumor characteristics, radiation seemed to be highly beneficial.

The researchers also found a subset of women for whom radiation did not benefit, and thus could be omitted from care regimen: those 75- 79 years of age who had their lymph nodes assessed and did not have high-grade tumors.

“I think the national guidelines, while well intended and important, may gloss over the certain nuances needed for making critical decisions with patients,” said Smith. “Our study may shed additional light on some of those nuances and provides data that physicians can use when talking to their patients about whether to go forward with radiation. Personally, having this data point, together with the previous findings, gives me the confidence to not routinely recommend radiation in women age 75 and over with non-high grade tumors.”

In addition to Smith, other MD Anderson authors on the study include: Thomas A Buchholz, M.D., professor and head of the Division of Radiation Oncology; Sharon Giordano, M.D., associate professor, Department of Breast Medical Oncology; Jeffrey M. Albert, M.D., resident, Department of Radiation Oncology; and Jing Jiang, Division of Quantitative Sciences. Other authors on the study include: I-Wen Pan, Ph.D. and Ya-Chen Tina Shih, Ph.D., both of The University of Chicago.

The study was funded, in part, by research grants from Varian Medical Systems, U.S. Department of Health and Human Services and the National Cancer Institute. Giordano and Smith are supported by a grant from the Cancer Prevention and Research Institute of Texas.